A variety of medical devices require weighted portions to provide pulling weights acted on by gravity to straighten, position, move and handle the devices. Such devices include weighted feeding tubes for the body, gastric tubes and the like which are passed into the body, with weights aiding in advancing the lightweight small diameter devices through body passageways employing the force of gravity. Generally, it is preferred that such devices be flexible and of small diameter. They often are formed of plastic or rubber and require dense and heavier portions than the plastic or rubber without significant increase in overall diameter. Significant increase in diameter could make the devices more difficult to use and to pass through the body orifices and channels.
The prior art has often used liquid metals, typically mercury, for the denser portion. The one advantage of liquid mercury is that it enables catheters to remain flexible since liquid is yieldable. Additional weight is provided because of the high specific gravity (13.6) of mercury. Mercury has certain disadvantages which include its toxicity which is of particular concern in medical devices. Moreover, its weight is limited and it is sometimes desirable to provide a higher bulk density for a required weight so as to conserve space taken up by the weight.